The behavioral and neural organization of learning and memory, and the relationship among brain, cognition and behavior, pose many important questions, with significant theoretical and clinical implications. Investigating these questions, will require analysis of both the behavioral and neural structure of learning and memory. The proposed research will investigate these issues by taking advantage of the exceptional spatial navigation ability of homing pigeons, which makes these birds an excellent, ecologically valid model for the study of the neurobiology of learning and memory. Studies examining the role of the hippocampal formation in homing pigeon navigation have revealed a complex picture that emphasizes the importance of this brain structure for the learning of navigational mechanisms. Results from a recently completed study suggest that the specific role of the hippocampal formation for spatial learning can be traced to its critical participation in a learning process in which the location of stimuli in space is learned using a directional reference system. The proposed research is designed to more completely explore this hypothesis by examining more broadly the effects of hippocampal lesions on learning. Spatial and nonspatial tasks will be employed. Some of the tasks require the use of directional reference if learning is to take place. The prediction is that hippocampal lesions will disrupt learning on only those tasks that involve a spatial reference. Because of the superb spatial learning ability of homing pigeons, the results will produce a great deal of basic information about the relationship among brain, behavior and cognition.